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BioChem Exam 2 > L20: Glycolysis > Flashcards

L20: Glycolysis Flashcards

1
Q

glycolysis involves a sequence of rxns that metabolizes?

A

1 molecule of glucose into:
2 molecules of pyruvate
2 ATP

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2
Q

is aerobic or anaerobic processes more efficient?

A

complete oxidation is more energy efficient than anaerobic glycolysis

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3
Q

what processes only use glucose for fuel?

A

in the brain under non-starvation conditions

only fuel that RBCs can use

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4
Q

sources of glucose in the diet

A

disaccharides – especially sucrose and lactose
starch
glycogen

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5
Q

glucose uptake

A

occurs via protein transporters called glucose transporters or GLUTs

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6
Q

GLUT1

A

ubiquitous but expressed highly in brain and RBCs

high affinity

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7
Q

GLUT2

A

main transporter in liver

low affinity

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8
Q

GLUT3

A

main transporter in neurons

high affinity

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9
Q

GLUT4

A

present in skeletal muscle, heart, adipose tissue

insulin dependent

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10
Q

which GLUT is the only one dependent upon insulin?

A

glut4

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11
Q

relate Km and affinity of GLUTs for glucose

A

low Km = high affinity
inverse relationship

glut1 and 3 have highest affinity
glut4 is moderate but regulated
glut3 is lowest

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12
Q

where does glycolysis occur in the body?

A

cytoplasm of eukaryotic cells

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13
Q

glycolysis is broken down into 2 stages

A
  1. trapping of glucose and its cleavage into 2 interconvertible 3-C molecules
  2. generation of atp
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14
Q

how does the first stage of glycolysis begin?

A

phosphorylation of glucose by hexokinase

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15
Q

how does the first stage of glycolysis end?

A

isomerization of dihydroxyacetone phosphate to glyceraldehyde 3-phosphate

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16
Q

stage 1, step 1

A

glucose is phosphorylated to
glucose-6-pi
atp consumed

enzymes: hexokinase and glucokinase

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17
Q

stage 1, step 2

A

G6P isomerized to fructose-6-pi

enzyme: phosphoglucoisomerase

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18
Q

stage 1, step 3

A

F6P phosphorylated to
fructose-1,6-biphosphate
atp consumed

enzyme: phosphofructokinase
* *rate limiting enzyme of glycolysis

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19
Q

what is the rate limiting step of glycolysis?

A

stage 1, step 3

enzyme phosphofructokinase

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20
Q

stage 1, step 4

A

F1,6BP broken into:
glyceraldehyde-3-pi and
dihydroxyacetone phosphate

enzyme aldose

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21
Q

stage 1, step 5

A

DHAP isomerized to G3P

enzyme: triose pi isomerase

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22
Q

GAP

A

glucose-3-pi or G3P

23
Q

second stage of glycolysis

A

nrg harnessed in GAP used to form ATP

24
Q

stage 2 steps

A
  1. GAPDH step
  2. phosphoglycerate kinase/mutase step
  3. enolase/pyruvate kinase step
25
Q

GAPDH step

A

oxidative phosphorylation of gap forming:
1,3-BPG

reduce NAD+ to NADH

26
Q

1,3-BPG

A

has a high phosphoryl-transfer potential

27
Q

NADH

A

contains a pair of ‘high energy’ electrons

e- sent to ETC plays role in oxidative phosphorylation

28
Q

phosphoglycerate kinase/mutase step

A

kinase converts 1,3-BPG to 3-PG

ADP is phosphorylated

mutase moves pi from 3rd to 2nd position 2-PG

**remember happens 2x = 2 atp

29
Q

enolase/pyruvate kinase step

A

dehydration of 2-pg by enolase
–forms PEP

pyruvate kinase transfers phosphoryl group from PEP to ADP

  • –forming ATP
  • *irreversible step
  • *2x
30
Q

PEP

A

an enol w/ high phosphoryl-transfer potential = unstable

is converted from unstable enol to pyruvate
—a stable ketone

31
Q

fates of pyruvate

A
  1. reduced to lactate w/ regeneration of NAD+

2. oxidized aerobically

32
Q

entry points of fructose

A

sucrose is a disaccharide of glucose and fructose

33
Q

entry points of galactose

A

lactose is a disaccharide of glucose and galactose

34
Q

fructose and galactose are converted into ?

A

glycolytic intermediates

fructose is quickly turned to fat in times of high nrg

35
Q

galactose metabolism ends in ?

A

glucose-6-pi

36
Q

major regulatory enzymes

A

hexokinase
phosphofructokinase
pyruvate kinase

37
Q

goal of glycolysis

A

in muscles to generate ATP during activity

ATP levels regulate glycolysis

38
Q

glycolysis of liver

A

to maintain blood glucose levels

provide building blocks for other pathways in response to biochemical diversity and need

39
Q

phosphofructokinase

A

activated by F-2,6-BP

inhibited by citrate

40
Q

glucokinase

A

no hexokinase in liver cells

glucokinase is not inhibited by glucose-6-pi
glucose permanently trapped

41
Q

pyruvate kinase is regulated by ?

A

allosteric effectors and covalent modification

42
Q

what is the main glucose transporter in the liver?

A

glut2

43
Q

what enzyme is the most important regulator of glycolysis?

A

phosphofructokinase

44
Q

which of the following is not an intermediate in the glycolytic pathway?

  1. 2-phosphoglycerate
  2. fructose 1,6-BP
  3. glucose-1-phosphate
  4. glyceraldehyde 3-phosphate
  5. phosphoenolpyruvate
A

glucose 1 phosphate

45
Q

high fructose consumption is linked to ?

A

fatty liver
insulin insensitivity
obesity
type 2 diabetes

46
Q

actions of fructokinase and triose kinase bypass ?

A

the most important regulatory step in glycolysis
phosphofructokinase-catalyzed rxn

in regards to how fructose is processed by the liver

47
Q

fructose derivatives in the liver

A

GAP an DHAP are processed by glycolysis to pyruvate and acetyl CoA in unregulated fashion

excess acetyl CoA converted to fatty acids
transported to adipose tissues

resulting in obesity and fatty liver

48
Q

lactose intolerance

A

inability to metabolize lactose due to deficiency in enzyme lactase

49
Q

lactase

A

enzyme that breaks down lactose to glucose and galactose

50
Q

galactosemia

A

disruption of galactose metabolism

inherited deficiency in galactose-1-phosphate uridyl transferase activity

51
Q

what is the treatment for galactosemia

A

removal of galactose and lactose from diet

52
Q

cataracts

A

clouding of the eye lens

non-active transferase in lens
aldose reductase causes accumulating galactose to be reduced to galactitol

53
Q

Warburg effect

A

aerobic glycolysis

tumor cells can metabolize glucose to lactate even in presence of oxygen

BioChem Exam 2 (6 decks)

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